The role of the hippocampus in behavioral arousal is being investigated by recording from single cells in the various regions of the hippocampus in rats during sleep with slow synchronized cortical activity, paradoxical sleep, quiet waking, spontaneous arousal from sleep, arousal from sleep by tonal stimuli, reactions to stimuli in the waking animal, during conditioning paradigms, and during presentations of noxious stimuli. The effects of lesions in the major input output pathways of the hippocampus on the behavior of the animal under the above conditions is also being investigated as well as the effects of such lesions on hippocampal neural activity.